Monoclonal antibodies have great therapeutic potential and play an important role in today's medical portfolio. During the last decade, a significant trend in the pharmaceutical industry has been the development of monoclonal antibodies (mAbs) as therapeutic agents for the treatment of a number of diseases, such as cancers, asthma, arthritis, multiple sclerosis etc. Monoclonal antibodies are predominantly manufactured as recombinant proteins in genetically engineered mammalian cell culture.
The Fc region of an antibody, i.e., the terminal ends of the heavy chains of antibody spanning domains CH2, CH3 and a portion of the hinge region, is limited in variability and is involved in effecting the physiological roles played by the antibody. The effector functions attributable to the Fc region of an antibody vary with the class and subclass of antibody and include binding of the antibody via the Fc region to a specific Fc receptor (“FcR”) on a cell which triggers various biological responses.
These receptors typically have an extracellular domain that mediates binding to Fc, a membrane spanning region, and an intracellular domain that may mediate some signaling event within the cell. These receptors are expressed in a variety of immune cells including monocytes, macrophages, neutrophils, dendritic cells, eosinophils, mast cells, platelets, B cells, large granular lymphocytes, Langerhans' cells, natural killer (NK) cells, and T cells. Formation of the Fc/FcγR complex recruits these effector cells to sites of bound antigen, typically resulting in signaling events within the cells and important subsequent immune responses such as release of inflammation mediators, B cell activation, endocytosis, phagocytosis, and cytotoxic attack. The ability to mediate cytotoxic and phagocytic effector functions is a potential mechanism by which antibodies destroy targeted cells. The cell-mediated reaction wherein nonspecific cytotoxic cells that express FcγRs recognize bound antibody on a target cell and subsequently cause lysis of the target cell is referred to as antibody dependent cell-mediated cytotoxicity (ADCC) (Ravetch, et al., Annu Rev Immunol 19 (2001) 275-290). The cell-mediated reaction wherein nonspecific cytotoxic cells that express FcγRs recognize bound antibody on a target cell and subsequently cause phagocytosis of the target cell is referred to as antibody dependent cell-mediated phagocytosis (ADCP). In addition, an overlapping site on the Fc region of the molecule also controls the activation of a cell independent cytotoxic function mediated by complement, otherwise known as complement dependent cytotoxicity (CDC).
For the IgG class of Abs, ADCC and ADCP are governed by engagement of the Fc region with a family of receptors referred to as Fcγ receptors (FcγRs). In humans, this protein family comprises FcγRI (CD64); FcγRII (CD32), including isoforms FcγRIIA, FcγRIIB, and FcγRIIC; and FcγRIII (CD16), including isoforms FcγRIIIA and FcγRIIIB (Raghavan, and Bjorkman, Annu. Rev. Cell Dev. Biol. 12 (1996) 181-220; Abes, et al., Expert Reviews VOL 5(6), (2009) 735-747). FcγRs are expressed on a variety of immune cells, and formation of the Fc/FcγR complex recruits these cells to sites of bound antigen, typically resulting in signaling and subsequent immune responses such as release of inflammation mediators, B cell activation, endocytosis, phagocytosis, and cytotoxic attack. Furthermore, whereas FcγRI, FcγRIIA/c, and FcγRIIIA are activating receptors characterized by an intracellular immunoreceptor tyrosine-based activation motif (ITAM), FcγRIM has an inhibition motif (ITIM) and is therefore inhibitory. Moreover, de Reys, et al., Blood, 81, (1993) 1792-1800 concluded that platelet activation and aggregation induced by monoclonal antibodies, like for example CD9, is initiated by antigen recognition followed by an Fc domain dependent step, which involves the FcγRII-receptor (see also: Taylor, et al., Blood 96 (2000) 4254-4260). While FcγRI binds monomeric IgG with high affinity, FcγRIII and FcγRII are low-affinity receptors, interacting with complexed or aggregated IgG.
The complement inflammatory cascade is a part of the innate immune response and is crucial to the ability for an individual to ward off infection. Another important Fc ligand is the complement protein C1q. Fc binding to C1q mediates a process called complement dependent cytotoxicity (CDC). C1q is capable of binding six antibodies, although binding to two IgGs is sufficient to activate the complement cascade. C1q forms a complex with the C1r and C1s serine proteases to form the C1 complex of the complement pathway.
In many circumstances, the binding and stimulation of effector functions mediated by the Fc region of immunoglobulins is highly beneficial, e.g. for a CD20 antibody, however, in certain instances it may be more advantageous to decrease or even to eliminate the effector function. This is particularly true for those antibodies designed to deliver a drug (e.g., toxins and isotopes) to the target cell where the Fc/FcγR mediated effector functions bring healthy immune cells into the proximity of the deadly payload, resulting in depletion of normal lymphoid tissue along with the target cells (Hutchins, et al., PNAS USA 92 (1995) 11980-11984; White, et al., Annu Rev Med 52 (2001) 125-145). In these cases the use of antibodies that poorly recruit complement or effector cells would be of a tremendous benefit (see also, Wu, et al., Cell Immunol 200 (2000) 16-26; Shields, et al., J. Biol Chem 276(9) (2001) 6591-6604; U.S. Pat. No. 6,194,551; U.S. Pat. No. 5,885,573 and PCT publication WO 04/029207).
In other instances, for example, where blocking the interaction of a widely expressed receptor with its cognate ligand is the objective, it would be advantageous to decrease or eliminate all antibody effector function to reduce unwanted toxicity. Also, in the instance where a therapeutic antibody exhibited promiscuous binding across a number of human tissues it would be prudent to limit the targeting of effector function to a diverse set of tissues to limit toxicity. Last but not least, reduced affinity of antibodies to the FcγRII receptor in particular would be advantageous for antibodies inducing platelet activation and aggregation via FcγRII receptor binding, which would be a serious side-effect of such antibodies.
Although there are certain subclasses of human immunoglobulins that lack specific effector functions, there are no known naturally occurring immunoglobulins that lack all effector functions. An alternate approach would be to engineer or mutate the critical residues in the Fc region that are responsible for effector function. For examples see PCT publications WO 2009/100309 (Medimmune), WO 2006/076594 (Xencor), WO 1999/58572 (Univ. Cambridge), US 2006/0134709 (Macrogenics), WO 2006/047350 (Xencor), WO 2006/053301 (Xencor), U.S. Pat. No. 6,737,056 (Genentech), U.S. Pat. No. 5,624,821 (Scotgen Pharmaceuticals), and US 2010/0166740 (Roche).
The binding of IgG to activating and inhibitory Fcγ receptors or the first component of complement (C1q) depends on residues located in the hinge region and the CH2 domain. Two regions of the CH2 domain are critical for FcγRs and complement C1q binding, and have unique sequences. Substitution of human IgG1 and IgG2 residues at positions 233-236 and IgG4 residues at positions 327, 330 and 331 greatly reduced ADCC and CDC (Armour, et al., Eur. J. Immunol. 29(8) (1999) 2613-2624; Shields, et al., J. Biol. Chem. 276(9) (2001) 6591-6604). Idusogie, et al., J. Immunol. 166 (2000) 2571-2575) mapped the C1q binding site for rituxan and showed that Pro329Ala reduced the ability of Rituximab to bind C1q and activate complement. Substitution of Pro329 with Ala has been reported to lead to a reduced binding to the FcγRI, FcγRII and FcγRIIIA receptors (Shields, et al., J. Biol. Chem. 276(9) (2001) 6591-6604) but this mutation has also been described as exhibiting a wildtype-like binding to the FcγRI and FcγRII and only a very small decrease in binding to the FcγRIIIA receptor (Table 1 and Table 2 in EP 1 068 241, Genentech).
Oganesyan, et al., Acta Cristallographica D64 (2008) 700-704 introduced the triple mutation L234F/L235E/P331S into the lower hinge and C2H domain and showed a decrease in binding activity to human IgG1 molecules to human C1q receptor, FcγRI, FcγRII and FcγRIIIA.
Still, there is an unmet need for antibodies with a strongly decreased ADCC and/or ADCP and/or CDC. Therefore, the aim of the current invention was to identify such antibodies. Surprisingly, it has been found that mutating the proline residue at Pro329 to glycine resulted in an unexpected strong inhibition of the FcγRIIIA and FcγRIIA receptor and in a strong inhibition of ADCC and CDC. Moreover, the combined mutation of Pro329 and for example L234A and L235A (LALA) lead to an unexpected strong inhibition of C1q, FcγRI, FcγRII and FcγRIIIA. Thus, a glycine residue appears to be unexpectedly superior over other amino acid substitutions, like alanine, for example, at position 329 in destroying the proline sandwich in the Fc/Fcγ receptor interface.